Kahuna Burger:
There have been people as far to the 'improv' side as to say that they don't allow a sense motive check during a roleplayed bluff unless the player specificly asks for one.
Actually, I do that. But I calculate a result of a sense motive check as if the player was "taking 8" (taking 10 with -2 for trusting the NPC). I do that because calling for a roll will influence the way the player reacts afterwards; even if he consciously tries to "forget" the roll, he will act differently than he would have before. Perhaps only minorly differently, but perhaps majorly - in both directions (trusting the NPC more than would be normal, or less).
If the DM has decided that this is the big fight scene, they may be unwilling to let any level of diplomacy run them off track.
Yeah. I actually try to envision a non-combat resolution for most of my encounters, just so that I know beforehand how tough that would be and what it would require.
But one reason that some DMs don't like to roll for skill checks is so they can do the exact same thing socially.
One example for this from my current campaign:
The players met a character who wasn't quite honest with them. Now, his skills were way better than theirs, so I wasn't too worried.
One player casts "read mind", and the NPC rolls a 1 on his Will save!
So I let them in on the dishonesty. And you know what? They still don't know why he lied, and whether the NPC isn't a good guy still.
Just goes to prove that some game-breakers don't really break the game.
But this is a little off-topic, because nobody here went out and said they would determine results beforehand. I just wanted to show off, I guess
Back to topic:
Sometimes I don't roll (as with the sense motive above). I just determine what would be cool, if it's a minor action. If my tough mojh player (a draconic-looking being) wants to stare intimidatingly at some bar patrons, they will be intimidated, because rolling then only has the potential of ruining fun, and it's window dressing more or less.
Berandor